Dynamic damper for steering system

Abstract

Disclosed is a dynamic damper for use in a steering system of an automotive vehicle, including a mounting member connectable to a steering column or a steering wheel of the steering system; and a plurality of secondary vibration systems independent of each other, each including a mass member and a spring member for elastically supporting the mass member to the mounting member. One of the plurality of secondary vibration systems has a natural frequency that is tuned to an idling vibration frequency band ranging from about 20 Hz to about 30 Hz, and another one of the plurality of secondary vibration systems has a natural frequency that is tuned to a natural frequency band of the steering system, which is larger than 30 Hz.

What is claimed is:  
     
       1. A dynamic damper for use in a steering system of an automotive vehicle, comprising: 
       a mounting member adapted to be fixed to a steering column or a steering wheel of the steering system; and  
       a plurality of secondary vibration systems each including a mass member and a spring member for elastically supporting said mass member with respect to said mounting member, said plurality of secondary vibration systems being independent of each other,  
       wherein at least one of said plurality of secondary vibration systems has a natural frequency that is tuned to an idling vibration frequency band ranging from about 20 Hz to about 30 Hz, and at least an other one of said plurality of secondary vibration systems has a natural frequency that is tuned to a natural frequency band of the steering system, which is larger than 30 Hz,  
       wherein in at least one of said secondary vibration systems, said spring member is formed as a unit independent of said mass member and including a coupling elastic member and a first and a second fixing member integrally bonded to said coupling elastic member, while said mass member is formed with a cutout or recess, and  
       wherein said first fixing member is fixed to an inside of said cutout or recess while the second fixing member is fixed to said mounting member so that said spring member is partially situated within said cutout or recess.  
     
     
       2. A dynamic damper according to  claim 1 , wherein the steering wheel of the steering system includes a reinforcing member made of light metal including an aluminum alloy and an magnesium alloy. 
     
     
       3. A dynamic damper according to  claim 1 , wherein said spring member of each of the secondary vibration systems whose natural frequencies are tuned to said idling vibration frequency band and said natural frequency band of the steering system, comprises an elastic support member adapted to undergo shear deformation in a direction perpendicular to a central axis of the steering column. 
     
     
       4. A dynamic damper according to  claim 3 , wherein said elastic support member of each of said secondary vibration systems whose natural frequencies are tuned to said idling vibration frequency band and said natural frequency of said steering system, has a circular shape in cross section in said direction perpendicular to said central axis of the steering column. 
     
     
       5. A dynamic damper according to  claim 3 , wherein at least one of said each of said secondary vibration systems is arranged such that said elastic support member has a principal elastic axis that is approximately in conformity with a principal inertia axis of said mass member in a direction in which said mass member and said mounting member are opposed to each other. 
     
     
       6. A dynamic damper according to  claim 1 , wherein said spring member of at least one of said plurality of secondary vibration systems comprises a plurality of elastic support members extending parallel to each other while having a circular shape in cross section. 
     
     
       7. A dynamic damper according to  claim 6 , wherein a vibrational load is applied to said dynamic damper in various radial directions approximately perpendicular to center axes of said plurality of elastic support members. 
     
     
       8. A dynamic damper according to  claim 6 , wherein said plurality of elastic support members are located close to an outer peripheral portion of said mass member rather than a center of gravity of said mass member, in a plane perpendicular to center axes of said plurality of elastic support members. 
     
     
       9. A dynamic damper according to  claim 6 , wherein a general principal elastic center of said plurality of elastic support members extends in a direction of central axes of said plurality of elastic support members, and is approximately in conformity with a principal inertia axis of said mass member. 
     
     
       10. A dynamic damper according to  claim 6 , wherein a general principal elastic center of said plurality of elastic support members extends parallel to a central axis of the steering column. 
     
     
       11. A dynamic damper according to  claim 1 , wherein said spring member of at least one of said plurality of said second vibration systems comprises three spring members which are made identical with each other. 
     
     
       12. A dynamic damper according to  claim 1 , wherein said mass member of at least one of said plurality of said second vibration systems has a circular shape in cross section perpendicular to a central axis of the steering column. 
     
     
       13. A dynamic damper according to  claim 1 , wherein said spring member of at least one of said plurality of said second vibration systems has a hollow cylindrical shape. 
     
     
       14. A dynamic damper according to  claim 1 , wherein in each of said secondary vibration systems, said mass member is formed with a plurality of said cutouts that are open in an outer peripheral portion of said mass member, respectively, and is elastically supported on said mounting member via a plurality of said spring members partially situated within said plurality of said cutouts, respectively. 
     
     
       15. A dynamic damper according to  claim 1 , wherein said coupling elastic member extends longitudinally with an approximately constant circular cross sectional shape, and said first and second fixing member integrally bonded to axially opposite end faces of said coupling elastic member, respectively, while at least one of said first and second fixing members is shaped as a bolt extending axially outwardly from a corresponding one of said axially opposite end faces said coupling elastic member. 
     
     
       16. A dynamic damper according to  claim 1 , wherein in each of said secondary vibration systems, said mass member is formed with said recess open in a central portion thereof, and is elastically supported on said mounting member via said spring member partially situated within said recess. 
     
     
       17. A dynamic damper according to  claim 1 , wherein said coupling elastic member extends longitudinally with an approximately constant circular cross sectional shape, and said first and second fixing member integrally bonded to axially opposite end portions of said coupling elastic member, respectively, while at least one of said first and second fixing members is shaped as a fixing plate extending in a direction perpendicular to an axis of said coupling elastic member, said fixing plate being provided with a plurality of through holes so that said fixing plate is partially embedded in a corresponding one of said axially opposite end portions of said coupling elastic member, and being fixed to said mass member or said mounting member at an peripheral portion thereof. 
     
     
       18. A dynamic damper according to  claim 1 , wherein said mass member includes a plurality of plates mutually superposed on each other, and said plurality of plates, except a most outer plate, are formed with through holes through which said coupling elastic member extends, and said most outer plate provides a closure of opening of said through holes so as to provide said recess. 
     
     
       19. A dynamic damper according to  claim 1 , wherein said mounting member is formed with a through hole, and said coupling elastic member extends through said through hole of said mounting member so that said second fixing member is fixed to a back surface of said mounting member, which is remote from said mass member.